Method of manufacturing pulp mold formed body

ABSTRACT

A method of producing a pulp molded article. The method feeds a pulp slurry to a cavity of a papermaking mold having a prescribed cavity shape to form a pulp preform including a main part having an opening and a separable part having a flange and connected to an edge of the opening. A pressing member is inserted into the preform, the pressing member is expanded to press the preform toward the papermaking surface, the preform is removed from the papermaking mold, and then the preform is cut at a joint between the separable part and the main part.

TECHNICAL FIELD

The present invention relates to a method of producing a pulp moldedarticle.

BACKGROUND ART

Production of pulp molded articles includes the step of dewatering awater-containing preform as obtained by a papermaking operation for thepurpose of, for example, improving handling properties and shorteningthe drying time. A known dewatering method comprises interposing thepreform between an outer mold of which the inner shape is substantiallythe same as the contour of a molded article to be produced and an innermold having a flexible film which expands into a shape substantially thesame as the inner shape of the molded article and pressing anddewatering the preform by making use of the expansion of the flexiblefilm as described in JP-A-7-223230.

In the above method, if the water-containing preform is out of the rightposition when pressed between the outer mold and the inner mold, or ifthe preform has an uneven thickness, it could follow that the preform,being fragile, is deformed or undergoes damages such as fall-off of thepulp fibers making up itself due to missregistered contact with themolds.

DISCLOSURE OF THE INVENTION

Accordingly, an object of the present invention is to provide a methodof stably producing a pulp molded article in which a water-containingpulp preform can be press-dewatered or press-dried without beingdeformed or damaged.

The present invention accomplishes the above object by providing amethod of producing a pulp molded article comprising the steps of:

feeding a pulp slurry to a cavity of a papermaking mold having aprescribed cavity shape to form a pulp preform on a papermaking surfaceof said cavity in such a manner that said preform comprises a main parthaving an opening and a separable part having a flange and connected tothe edge of said opening,

feeding a pressurizing fluid into said preform to dewater said preform,

removing said preform from said papermaking mold,

putting said preform into a cavity of a heating mold having a prescribedcavity shape,

inserting an expandable pressing member into said preform,

feeding a prescribed fluid into said pressing member to expand saidpressing member thereby to dry said preform while pressing said preformby the expanded pressing member toward said papermaking surface,

removing the dried preform from said heating mold, and then

cutting said preform at a joint between said separable part and saidmain part (hereinafter referred to as a first aspect of the invention).

The present invention also accomplishes the above object by providing amethod of producing a pulp molded article comprising the steps of:

feeding a pulp slurry to a cavity of a papermaking mold having aprescribed cavity shape to form a pulp preform on a papermaking surfaceof said cavity in such a manner that said preform comprises a main parthaving an opening and a separable part having a flange and connected tothe edge of said opening,

inserting an expandable pressing member into said preform,

feeding a prescribed fluid into said pressing member to expand saidpressing member thereby to press said preform toward said papermakingsurface by the expanded pressing member,

removing said preform from said papermaking mold, and then

cutting said preform at a joint between said separable part and saidmain part (hereinafter referred to as a second aspect of the invention).

The present invention also provides a method of producing a pulp moldedarticle comprising the steps of:

forming a preform having a prescribed shape by a wet papermakingprocess,

putting said preform into a cavity of a heating mold having a prescribedcavity shape,

inserting an expandable pressing member into said preform,

feeding a prescribed fluid into said pressing member to expand saidpressing member thereby to press said preform by the expanded preformtoward a surface of said cavity to shape said preform into a main parthaving an opening and a separable part having a flange and connected tothe edge of said opening,

removing the resulting preform comprising said main part and saidseparable part from said heating mold, and then

cutting said preform at a joint between said separable part and saidmain part (hereinafter referred to as a third aspect of the invention).

The present invention further provides an apparatus for producing a pulpmolded article comprising:

a papermaking mold having a cavity of a prescribed shape,

means for feeding a pulp slurry to said cavity,

an expandable pressing member which is to be inserted into a pulppreform formed in said cavity and comprising a main part having anopening and a separable part having a flange and connected to the edgeof said opening,

means for inserting said pressing member,

means for feeding a prescribed fluid into said pressing member,

means for removing said preform from said papermaking mold, and

means for cutting said preform at a joint between said separable partand said main part.

The present invention further provides another apparatus for producing apulp molded article comprising:

a heating mold having a cavity of a prescribed shape,

means for putting a pulp preform into said heating mold, said pulppreform having been formed by a wet papermaking process and comprising amain part having an opening and a separable part having a flange andconnected to the edge of said opening,

an expandable pressing member which is to be inserted into said preform,

means for inserting said pressing member,

means for feeding a prescribed fluid into said pressing member,

means for removing said preform from said heating mold, and

means for cutting said preform at a joint between said separable partand said main part.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a) shows the steps of feeding a pulp slurry and dewatering bysuction. FIG. 1(b) shows the step of dewatering by feeding apressurizing fluid. FIG. 1(c) shows the step of opening the papermakingmold.

FIG. 2(a) shows the step of inserting a pressing member. FIG. 2(b) showsthe step of heat drying. FIG. 2(c) shows the step of opening the heatingmold. FIG. 2(d) shows the step of cutting the dried preform.

FIG. 3 minutely shows the fixing part.

FIG. 4(a) shows the steps of feeding a pulp slurry and dewatering bysuction. FIG. 4(b) shows the step of inserting a pressing member. FIG.4(c) shows the step of dewatering by pressing. FIG. 4(d) shows the stepof opening the papermaking mold.

BEST MODE FOR CARRYING OUT THE INVENTION

The first aspect of the invention will be described based on itspreferred embodiments with reference to the drawings. The presentembodiment represents production of a bottle-shaped pulp molded article(hereinafter also referred simply to as is a molded article) with anopen neck, of which the body has a larger diameter than the neck. FIGS.1(a) through 1(c) depict in order the steps of papermaking anddewatering according to the pulp molded article production method of thepresent invention. FIG. 1(a) is the steps of feeding a pulp slurry anddewatering by suction; FIG. 1(b) is the step of dewatering by feeding apressurizing fluid; and FIG. 1(c) is the step of opening the papermakingmold.

A production apparatus used to carry out the production method accordingto this embodiment comprises a papermaking mold having a cavity of aprescribed shape, a means for feeding a pulp slurry into the cavity, anda means for feeding a pressurizing fluid into a preform formed in thecavity.

A papermaking mold 1 shown in FIG. 1(a) is prepared. The papermakingmold 1 is made up of a pair of split pieces 2 and 3, the pieces 2 and 3being joined together to form a cavity 4 having a prescribed shape. Theinner wall of the cavity 4 is covered with a papermaking net (not shown)having a prescribed mesh size. Each of the pieces 2 and 3 has aplurality of interconnecting passageways 5 which connect the inside (theinner wall of the cavity 4) to the outside of the mold. Eachinterconnecting passageway 5 is connected to a suction means (not shown)such as a suction pump. The cavity 4 connects to the outside of thepapermaking mold 1 through a slurry feed passage 6.

The cavity 4 is composed of a cavity part 4 a corresponding to the mainpart of a pulp molded article with an opening and a cavity part 4 bcorresponding to a separable part connected to the edge of the openingof the main part. The cavity part 4 a (corresponding to the main part)is shaped to provide a bottle-shaped pulp molded article having an openneck, a body, and a bottom. The cavity part 4 b (corresponding to theseparable part) is shaped to provide a separable part 7 having alaterally extending flange 7 c and an upright wall 7 d standing up fromthe periphery of the flange 7 c. A ridge 11 is formed as a boundarybetween the cavity part 4 a and the cavity part 4 b. The ridge 11 isannular around the whole inner circumference of the cavity 4. The ridge11 has a triangular cross-section.

With this state of the split mold 1, a feed nozzle 12 is insertedthrough the slurry feed passage 6, and a predetermined amount of a pulpslurry is poured into the cavity 4 through the feed nozzle 12. At thesame time, the cavity 4 is evacuated by suction through theinterconnecting passageways 5 toward the outside of the papermaking mold1, whereby the water content of the pulp slurry is sucked up, and pulpfiber is built up on the papermaking surface, i.e., the papermaking netcovering the inner wall of the cavity 4. As a result, there is formed awater-containing preform 7 as a deposit of pulp fiber on the papermakingnet. A predetermined amount of water (diluent water) can be injectedinto the cavity 4 in the initial stage and/or the final stage of formingthe preform 7 to thin the pulp slurry in the cavity 4 so as to preventthickness unevenness of the preform 7 effectively. The initial stage offorming is the stage when the amount of pulp having been fed into thecavity 4 is not more than 30%, particularly not more than 20%, of thetotal amount of pulp necessary for preform formation. The final stage offorming is the stage when the amount of pulp having been fed into thecavity 4 is 70% or more, particularly 80% or more, of the total amountof pulp necessary for preform formation. The amount of diluent water tobe fed is preferably such that the concentration of the pulp slurry isreduced to 80% or lower, particularly 20 to 60%.

As shown in FIG. 1(a), the preform 7 is composed of a main part 7 a withan opening and a separable part 7 b connected to the edge of theopening. An annular recess 13 corresponding to the ridge 11 on the innerwall of the cavity 4 of the papermaking mold 1 is formed at the jointbetween the main part 7 a and the separable part 7 b. The recess 13 isused for registration in cutting the main part 7 a and the separablepart 7 b apart.

The feed nozzle 12 is used as a means for feeding the pulp slurry and apressurizing fluid described later. The feed nozzle 12 has a fittingplate 12 a, a nozzle 12 b vertically piercing the fitting plate, athree-way valve 12 c attached to the upper end of the nozzle 12 b, and aslurry feed pipe 12 d and a pressurizing fluid feed pipe 12 e bothconnected to the three-way valve 12 c. On switching the three-way valve12 c, the nozzle 12 b is connected to either the slurry feed pipe 12 dor the pressurizing fluid feed pipe 12 e. While the pulp slurry ispoured into the cavity 4, the nozzle 12 b is connected to the slurryfeed pipe 12 d. The fitting plate 12 a is fitted into the slurry feedpassage 6 to close the slurry feed passage 6.

Molding of the preform 7 is performed such that the main part 7 a, onepart of the preform 7, has a bottle shape having an open neck, a body,and a bottom and that the separable part 7 b, the other part of thepreform 7, has a laterally extending flange 7 c and an upright wall 7 dstanding up from the periphery of the flange 7 c.

The resulting preform 7 is subjected to a dewatering step. As shown inFIG. 1(b), the papermaking mold 1 is evacuated through theinterconnecting passageways 5. In this state, with the feed nozzle 12remaining fixed at the position for papermaking, the three-way valve 12c is switched over to connect the nozzle 12 b to the pressurizing fluidfeed pipe 12 d, and a prescribed pressurizing fluid is supplied from apressurizing fluid source (not shown) to the cavity 4. As statedpreviously, since the slurry feed passage 6 is clogged by the fittingplate 12 a, the cavity 4 is hermetic. The term “hermetic” as used hereindoes not mean that the cavity 4 is completely hermetic but that thecavity 4 is airtight enough to increase its inner pressure above aspecific level described later by introducing a pressurizing fluid. Theintroduced pressurizing fluid penetrates the preform 7 and is dischargedoutside through the interconnecting passageways 5.

Pressurizing fluids which can be used include steam and superheatedsteam (hereinafter inclusively referred to as steam). It is particularlypreferred to use superheated steam. By blowing steam, the temperature ofwater present in the preform 7 rises instantaneously by the heattransfer in condensation of steam thereby to reduce the viscosity andthe surface tension of water. As a result, the water content in thepreform 7 is blown off instantaneously and very efficiently therebyachieving improved dewatering efficiency. Not relying chiefly on heatexchange, this dewatering technique is extremely energicallyadvantageous. Moreover dewatering completes instantaneously, providing areduction of dewatering time. Because an elastic pressing member, whichis used in the heat drying step hereinafter described, is not used fordewatering, the time for mechanical operations involved in using apressing member, such as insertion into the cavity, is omitted,resulting in a reduction of the time for mechanical operations. Further,because the blowing pressure is lower than the pressure applied in pressdewatering, there is obtained an additional advantage that thepapermaking net hardly leaves its marks on the surface of the resultingpreform 7 to provide a molded article with a good appearance.

Steam are preferably introduced to increase the inner pressure of thecavity 4 to 98 kPa or greater, particularly 196 kPa or greater,especially 294 kPa or greater. While better results are obtained with ahigher inner pressure of the cavity 4, the upper limit of the pressurethat pays is about 980 kPa because the water removal efficiencygradually approaches saturation with a pressure increase. The term“(inner) pressure in the cavity 4” as used herein means a steam pressuredifference between the inlet and the outlet of the cavity 4.

It is preferable to start introducing steam while the slurry stays inthe cavity 4 or while the diluent water, which has been fed into thecavity 4 in the final stage of forming the preform 7, stays in thecavity 4, whereby the water content in the cavity 4 is expelled out ofthe mold to shorten the dewatering time. Steam is preferably blown forabout 2 to 20 seconds, particularly about 3 to 15 seconds. Dewateringcompletes in an extremely short time. By this dewatering step, thepreform that has had a water content of 75 to 80% by weight beforedewatering is dewatered to a water content of about 40 to 70% by weight.

Where superheated steam is used, a sufficient degree of superheating issuch that the inner pressure of the mold is increased to or above theabove-specified value and that the steam is not condensed before beingblown into the mold. Steam may be overheated sufficiently, but thedewatering effect is not improved correspondingly.

In addition to the above-mentioned steam, compressed air is also usefulas a pressurizing fluid for dewatering the preform 7. By blowingcompressed air, a physical mechanism which does not chiefly rely on heatexchange works to remove the water content from the wet preform 7instantaneously. Compressed air is preferably blown to increase thepressure of the cavity 4 to 196 kPa or higher, particularly 294 kPa orhigher. The upper limit of the pressure is about 1471 kPa for the samereasons as with steam. The time for blowing compressed air is preferably10 to 60 seconds, particularly 15 to 40 seconds. The pressure (initialpressure) of compressed air is not particularly limited as long as themold inner pressure may be increased to or above the above-recitedlevel. The detailed description concerning steam appropriately appliesto the particulars of compressed air that are not described here.

While steam and compressed air may be used individually, a combined useof both is preferred for dewatering efficiency. It is particularlypreferred to introduce steam followed by compressed air for thefollowing reason. If the steam blowing time is long, there can result alarge water content variation in the vertical direction of the preform7. In order to avoid this, it is effective to first blow steam tosufficiently elevate the temperature of water contained in the preformand then blow compressed air. When steam and compressed air are blown inthis order, steam are preferably blown at a pressure of 98 kPa orhigher, particularly 196 kPa or higher, especially 294 kPa or higher,for 2 to 20 seconds, particularly 3 to 15 seconds, and compressed air ispreferably blown at a pressure of 196 kPa or higher, particularly 294kPa or higher, for 2 to 25 seconds, particularly 5 to 20 seconds. It ispreferred for dewatering efficiency that blowing steam be continuouslyfollowed by blowing compressed air.

After the preform 7 is dewatered to a prescribed water content, the feedof the pressurizing fluid is stopped, and the feed nozzle 12 is takenout of the papermaking mold 1 as shown in FIG. 1(c). The papermakingmold 1 is opened, and the preform 7 having been dewatered to theprescribed water content is removed by means of a prescribed handlingunit.

The preform 7 taken out is then subjected to the step of heat drying.FIGS. 2(a) to 2(c) show the heat drying step in order. FIG. 2(a) is thestep of inserting a pressing member; FIG. 2(b) the step of heat drying;FIG. 2(c) the step of opening the heating mold; and FIG. 2(d) the stepof cutting the dried preform.

The heat drying step is carried out by use of a production apparatuscomprising a heating mold having a cavity of a prescribed shape, a meansfor fitting the pulp preform formed in the papermaking mold 1 into theheating mold, an expandable pressing member which is to be inserted intothe preform 7, a means for inserting the pressing member, a means forfeeding a prescribed fluid into the pressing member, a means forremoving the preform 7 from the heating mold, and a means for cuttingthe preform 7 at the joint between the separable part 7 b and the mainpart 7 a.

A heating mold 21 which is made up of a pair of split pieces 22 and 23is separately prepared, the pieces 22 and 23 being joined together toform a cavity 24 having a shape in conformity to the contour of a moldedpreform to be produced. The heating mold 21 is previously heated to aprescribed temperature. In this embodiment, the cavity shape of theheating mold 21 is the same as that of the papermaking mold. Therefore,a ridge 27 is formed on the cavity wall of the heating mold 21 at theposition corresponding to the joint between the separable part 7 b andthe main part 7 a of the preform similarly to the papermaking mold 1.The water-containing preform having been dewatered to the prescribedwater content is fitted into the cavity of the heated heating mold bymeans of a prescribed handling unit. There is not a net on the innersurface of the cavity 24. Each of the split pieces 22 and 23 has aplurality of interconnecting passageways 25 which connect the insidethereof (the inner wall of the cavity 24) and the outside. Eachinterconnecting passageway 25 is connected to a suction means (notshown), such as a suction pump. The cavity 24 connects to the outside ofthe heating mold 21 through a pressing member insertion passage 26.

While the heating mold 21 is sucked from the inside toward the outsidethrough the interconnecting passageways 25, a pressing member 8, whichis a hollow bag, is inserted into the preform 7 through the pressingmember insertion passage 26 as shown in FIG. 2(a). The pressing member 8is used to press and dry the preform 7.

When the pressing member 8 is accidentally inserted into the preform 7at an inaccurate position and goes down toward the bottom of the preform7 while touching the pulp fibers of the separable part 7 b, the flange 7c behaves an anchor on the pulp fibers which go down toward the bottomof the preform 7 c. The pulp fibers touched by the pressing member 8still stay at the original position of the separable part 7 b. As aresult, the main part 7 a has no defect arising from the pulp fiberstouched by the pressing member 8 because the separable part 7 b is anunnecessary part once the main part 7 a is obtained. The anchor effectof the flange 7 c is more enhanced by the presence of the upright wall 7d formed on the periphery of the flange 7 c.

The separable part 7 b also has an advantage in making a multilayeredmolded article. In the production of the multilayered molded article,two or more slurries are employed. In general, undesirable mixing of theslurries tends to occur near the end of an open neck of the preform 7.The mixing of the slurries jeopardizes the formation of a clearmultilayered structure. In the present invention, the separable part 7 boccupies the end of the open neck. Therefore, even if the separable part7 b does not have a clear multilayered structure, the main part 7 a maybe highly likely to have a clear multilayered structure. The separablepart 7 b is unnecessary once the target molded article is obtained. As aresult, the production yield of the multilayered molded article isimproved by the presence of the separable part 7 b.

The separable part 7 b provides an additional advantage in theproduction of the pulp molded article. The separable part is useful as ahandle to be gripped by a handling unit which transfers the preform 7 toa next production step of the molded article.

The pressing member 8 has a supporting member 10 inserted therein. Thesupporting member 10 is a cylinderical pipe having many holes 10 a inits lateral surface. The lower end 10 b of the supporting member 10 isopen. The pressing member 8 has a projection 8 b of a prescribed shapeon the inner side of its bottom, and the projection 8 b is fitted intothe lower open end 10 b. The pressing member is inserted into thepreform 7 with the supporting member 10. The insertion of the pressingmember 8 into the preform 7 may be smooth because the supporting member10 functions as a spine of the pressing member 8. The supporting member8 can prevent a swaying motion of the pressing member 8 during theinsertion process. Further, expansion of the pressing member 8hereinafter described can be performed uniformly, and the preform 7 canbe press dried uniformly.

As shown in FIG. 2(a), the pressing member 8 and the supporting member10 are inserted into the preform 7 in a state fixed to a fixing part 9as a means for inserting the pressing member 8. FIG. 3 minutelyillustrates the structure of the fixing part 9.

As shown in FIG. 3, the fixing part 9 is made of a fitting plate 9 a, apressing bush 9 b, and a holder 9 c.

The fitting plate 9 a is a flat plate having a through-hole in itscenter. The diameter of the through-hole is approximately the same asthat of the supporting member 10. The supporting member 10 is insertedthrough the through-hole and fixed therein. The inner wall of thethrough-hole has an annular groove, in which an O-ring 9 d is fitted tokeep air-tightness between the through-hole and the supporting member.

The pressing bush 9 b is a cylinder having a flange 9 e extendinglaterally from the upper end. The upper open end of the hollow bagpressing member 8 is clamped between the upper face of the flange 9 eand the lower face of the fitting plate 9 a.

The holder 9 c is fixed to the fitting plate 9 a by fixing screws 9 fthereby to hold the flange 9 e of the pressing bush 9 b.

The pressing member 8 is made of an expandable material. The term“expandable” as used herein for the pressing member means that (1) thepressing member 8 elastically stretches and contracts to change itscapacity or (2) the pressing member 8 is not stretchable per se but iscapable of changing its capacity with a fluid fed inside thereof ordischarged outside. The former expandable member is made of an elasticmaterial, such as natural rubber, urethane rubber, fluororubber,silicone rubber and elastomers. The latter expandable member can be offlexible materials, such as plastic materials (e.g., polyethylene andpolypropylene), films of such plastic materials having aluminum orsilica deposited thereon, films of such plastic materials laminated withaluminum foil, papers, fabrics, and the like. In the present embodiment,a balloon-like oblong bag made of an inflatable elastic material is usedas a pressing member 8.

As shown in FIG. 2(b), when the pressing member 8 is completelyinserted, the lower end of the pressing member 8 is positioned near thebottom of the preform 7. In this state, a prescribed pressurizing fluidis fed into the supporting member 10 from its source (not shown), i.e.,a feeder of the pressurizing fluid, as shown in the Figure. Thepressurizing fluid fed is supplied inside the pressing member 8 throughthe holes 10 a made on the lateral surface of the supporting member 10.Simultaneously with the pressurizing fluid feed, the split pieces 22 and23 are sucked from the outside. The pressing member 8 is thus inflated.

The preform 7 is pressed by the inflated pressing member 8 toward theinner surface of the cavity 24, whereby the preform 7 dries, and theinner configuration of the cavity 24 is transferred to the preform 7 atthe same time. Since the preform 7 is pressed from its inside to theinner wall of the cavity 24, the shape of the cavity 24 can betransferred to the preform 7 with high precision however complicated itmay be, and a deep molded article having an almost upright body can beproduced easily. The pressurizing fluid which can be used to expand thepressing member 8 includes air (pressurizing air), hot air (heatedpressurizing air), superheated steam, oil (heated oil), and othervarious liquids. From the standpoint of operating convenience, it ispreferable to use air, hot air or superheated steam. The pressurizingfluid is preferably fed under a pressure of 0.01 to 5 MPa, particularly0.1 to 3 MPa.

After the preform has dried sufficiently, the fluid is withdrawn fromthe pressing member 8, whereby the pressing member 8 shrinks to itsoriginal size as shown in FIG. 2(C). The shrunken pressing member 8 andthe supporting member 10 are then removed from the molded article 7, andthe heating mold 21 is opened to take out the molded article by means ofa prescribed handling unit.

As shown in FIG. 2(d), the molded article 7 taken out of the heatingmold is cut with a prescribed cutting means at the joint connecting theseparable part 7 b and the main part 7 a into the separable part 7 b andthe main part 7 a. There is thus obtained a pulp molded article 7 a as afinal product. A rotary knife can be used, for example, as a cuttingmeans. Since the joint has the annular recess 13 corresponding to theridge 11 of the papermaking mold 1 as described previously, it is easyto position a rotary knife in cutting thereby reducing occurrence ofreject articles. The separable parts 7 b that have been cut off arereused as a material of molded articles.

The second aspect of the invention is described based on its preferredembodiments with reference to FIGS. 4(a) through 4(d). The second aspectof the invention will be described only with regard to differences fromthe first one. The detailed description about the first aspectappropriately applies to the particulars of the second aspect that arenot described here. The members in FIGS. 4(a) to 4(d) that are the sameas those in FIGS. 1 to 3 are given the same reference numerals as in thelatter. The particular embodiment described here represents productionof a bottle-shaped molded article with an open neck, of which the bodyhas a larger diameter than the neck similarly to the first aspect of theinvention. FIGS. 4(a) through 4(d) depict in order the steps ofpapermaking and dewatering according to the pulp molded articleproduction method of the present invention. FIG. 4(a) is the steps ofpouring a pulp slurry and dewatering by suction; FIG. 4(b) is the stepof inserting a pressing member; FIG. 4(c) is the step of pressdewatering; and FIG. 4(d) is the step of opening the papermaking mold.

An apparatus which can be used to carry out the production method of thepresent embodiment comprises a papermaking mold having a cavity of aprescribed shape, a means for feeding a pulp slurry to the cavity, anexpandable pressing member which is to be inserted into a preform formedin the cavity, a means for inserting the pressing member, a means forfeeding a prescribed fluid into the pressing member, and a means forremoving the molded article from the papermaking mold.

As shown in FIG. 4(a), a predetermined amount of a pulp slurry is pouredinto the cavity 4 of the papermaking mold 1 through the slurry feedpassage 6 by a pulp slurry feeding means (not shown). At the same time,the cavity 4 is evacuated by suction through the interconnectingpassageways 5 toward the outside of the papermaking mold 1, whereby thewater content of the pulp slurry is sucked up, and pulp fiber is builtup on the papermaking surface, i.e., the papermaking net covering theinner wall of the cavity 4. As a result, there is formed on thepapermaking net a water-containing preform 7 composed of a main part 7 awith an opening and a separable part 7 b connected to the edge of theopening. Similarly to the first aspect of the invention, a predeterminedamount of diluent water may be injected into the cavity 4 in the initialstage and/or the final stage of forming the preform 7 to thin the pulpslurry in the cavity 4.

The resulting preform 7 is subjected to a press-dewatering step. Asshown in FIG. 4(b), a pressing member 8 is inserted into the preform 7while evacuating the papermaking mold 1 through the interconnectingpassageways 5 from the inside to the outside. The pressing member 8 isthe same as used in the first aspect of the invention. This does notmean that the pressing member 8 to be used here should be of the samematerial, shape, etc. as those used in the first aspect. While, in thefirst aspect, the pressing member 8 is used for press drying thedewatered preform, the one used in the second aspect is for pressdewatering the preform 7.

Prior to inserting the pressing member 8, a pressurizing fluid, such ascompressed air, may be introduced into the cavity 4 while the slurryremains in the cavity 4 or while the diluent water, which has been fedto the cavity 4 in the final stage of preform 7 formation, remains inthe cavity 4 thereby to expel the water content in the cavity 4 out ofthe mold. Where compressed air is blown, the blowing pressure and timecan be the same as those used for compressed air that is used in thedewatering step according to the first aspect of the invention.

In the second aspect of the invention, the separable part 7 b of thepreform 7 has a laterally extending flange 7 c similarly to the firstaspect. Therefore, even if the pressing member 8 is inserted into thepreform 7 while touching some part of the preform 7, it can be insertedinto the preform 7 without causing deformation of, or damage to, themain part 7 a. In particular, the preform 7 as obtained by papermakingis has a lower strength than the dewatered preform 7 because of itshigher water content and is therefore easily deformed or damaged on aslight contact with the pressing member 8. Such deformation and damagecan be prevented effectively by the flange 7 c.

The pressing member 8 has a supporting member 10 inserted therein. Thepressing member 8 and the supporting member 10 are inserted into thepreform 7 while being fixed to the fixing part 9 as shown in FIG. 4(b).The details of the supporting member 10 and the fixing part 9 are thesame as those in the first aspect of the invention.

When the pressing member 8 is inserted completely, the lower end of thepressing member 8 is positioned near the bottom of the preform 7. Inthis state, a prescribed pressurizing fluid is fed into the supportingmember 10 from its source (not shown), i.e., a feeder of thepressurizing fluid, as shown in FIG. 4(c). Simultaneously with thepressurizing fluid feed, the splits 2 and 3 are evacuated from theoutside. The pressing member 8 is thus expanded.

The water-containing preform 7 is pressed to the papermaking surface,i.e., the inner wall of the cavity 4, by the expanded pressing member 8.As a result, the preform 7 is press dewatered, and the inner shape ofthe cavity 4 is transferred to the preform 7. The fluid used to expandthe pressing member 8 and the pressure of feeding the fluid are the sameas those used in the first aspect of the invention.

After the preform 7 is dewatered to a prescribed water content, and theinner shape of the cavity 4 is sufficiently transferred to the preform7, the fluid is withdrawn from the pressing member 8 to shrink thepressing member to its original size as shown in FIG. 4(d). The shrunkenpressing member 8 and the supporting member 10 are taken out of thepreform 7, and the papermaking mold 1 is opened to remove the preform 7dewatered to the prescribed water content by means of a prescribedhandling unit.

The preform taken out is subjected to the step of heat drying. The heatdrying step is carried out in the same manner as in the first aspect ofthe invention. The dried preform is removed from the heating mold andcut at the recess, the joint between the separable part and the pulpmolded article (main part), similarly to the first aspect of theinvention.

The third aspect of the invention will now be described. The thirdaspect will be described only with regard to differences from the firstand second ones. The detailed description about the first aspectappropriately applies to the particulars of the third aspect that arenot described here.

In the third aspect of the invention, a preform having a prescribedshape is made by a prescribed wet papermaking process. The wetpapermaking process includes not only the papermaking technique used inthe first and the second aspects but other conventionally knownpapermaking processes. The shape of the preform is not particularlylimited but is preferably close to the shape of a preform formed in thestep of heat drying described later which is composed of a pulp moldedmain part and a separable part.

The preform formed by a wet papermaking process is subjected to aprescribed dewatering step. Dewatering can be carried out by anappropriate method including the dewatering method using a pressurizingfluid which is used in the first aspect, the press dewatering methodusing a pressing member which is used in the second aspect, and otherconventionally known dewatering methods. By the dewatering step, thepreform is dewatered to such a water content which makes the preformeasy to handle.

The preform having a prescribed water content is then subjected to thestep of heat drying. The heat drying step is performed by using aheating mold having a cavity whose shape corresponds to the contour of apreform of desired configuration which is composed of a main part and aseparable part. The same heating mold as used in the first and thesecond aspects of the invention can be used, for example.

The preform having been dewatered to the prescribed water content is putinto the cavity, and an expandable pressing member is inserted into thepreform. A prescribed fluid is fed into the pressing member to expandthe pressing member, and the preform is pressed toward the cavity wallby the expanded pressing member. The same pressing member and fluid usedin the first and the second aspects can be used.

As a result of pressing the preform to the cavity wall by the pressingwith the pressing member, the pressed preform is shaped into a preformcomposed of a main part with an opening and a flanged separable partconnected to the edge of the opening while being dried by the heat. Theconfiguration, such as the shape, of the flange can be the same as thatin the first and the second aspects of the invention. Thereafter, theseparable part and the main part are cut apart to obtain a pulp moldedarticle as a final product.

The present invention is not limited to the above-described embodiments.For example, while the flange 7 c of the separable part 7 b in theaforementioned embodiments has the upright wall 7 d on its periphery,the upright wall 7 d may be omitted as far as the flange 7 c exhibits asufficient pulp fiber catching action. The flange 7 c, which extendshorizontally, may be tapered to have an upward slope to the periphery.

The flange 7 c may be discontinuous as long as a sufficient pulp fibercatching action is exerted.

In the drying step, a pressing member to be used may have a larger sizethan the opening of the preform in order to improve durability of thepressing member against repeated use. In this case, too, the pulp moldedarticle can be prevented from deformation or damage even if the pressingmember touches the flange because the preform having been dewatered tothe prescribed water content has high strength. As a result, the step ofshrinking the pressing member prior to the insertion into the preformcan be omitted, which leads to a reduction of time required formechanical operation.

While the papermaking mold 1 used in the aforementioned embodiments ismade up of a pair of pieces 2 and 3, it may be composed of three or moresplit pieces in accordance with the shape of the molded article. Thesame applies to the heating mold.

While the papermaking mold and the drying mold used in the aboveembodiments have a continuous annular ridge 11, the ridge 11 may bediscontinuous. In this case, the recess 13 corresponding to the ridge 11which is formed on the preform is also discontinuous.

The particulars of the above-described embodiments are appropriatelyinterchangeable with each other.

The production methods according to the present invention areparticularly effective for the manufacture of bottle-shaped moldedarticles. They are applicable as well to the manufacture of cartons,cushioning materials, and molded articles of other shapes. They areapplicable to the manufacture of not only containers for holdingcontents but molded articles of various shapes as freely designed, suchas ornaments.

INDUSTRIAL APPLICABILITY

According to the methods of producing a pulp molded article according tothe present invention, a pulp molded article can be produced stablybecause a water-containing preform can be press dewatered or pressheated without being deformed or damaged.

In carrying out multilayer papermaking, a pulp molded article having amultilayered structure can be formed stably to attain an increasedyield.

According to the methods of the invention, a pulp molded preform hasimproved handling properties in the production steps.

1. A method of producing a pulp molded article comprising: feeding apulp slurry to a cavity of a papermaking mold having a prescribed cavityshape to form a pulp preform on a papermaking surface of said cavitysuch that said preform comprises a main part having an open neck and abody with a diameter greater than a diameter of said open neck and aseparable part having a flange and connected to an edge of said openneck; inserting an expandable pressing member into said preform from aside of said separable part; feeding a prescribed fluid into saidpressing member to expand said pressing member thereby to press saidpreform toward said papermaking surface by the expanded pressing member;removing said preform from said papermaking mold; and then cutting saidpreform at a joint between said separable part and said main part. 2.The method of producing a pulp molded article according to claim 1,wherein said pressing member has a supporting member inserted thereinwith a prescribed part of said pressing member being fixed to aprescribed part of said supporting member, and said pressing member isinserted into said preform while being supported by said supportingmember.
 3. The method of producing a pulp molded article according toclaim 1, wherein said preform is formed such that said main part assumesa shape of a bottle having an open neck, a body, and a bottom.
 4. Themethod of producing a pulp molded article according to claim 1, whereinthe preform is formed such that said separable part has an upright wallstanding from a periphery of said flange.
 5. An apparatus for carryingout the method of producing a pulp molded article according to claim 1comprising: a papermaking mold having a cavity of a prescribed shape;means for feeding a pulp slurry to said cavity; an expandable pressingmember configured to be inserted into a pulp preform formed in saidcavity; means for feeding a prescribed fluid into said pressing member;means for removing said preform from said papermaking mold; and meansfor cutting said preform at a joint between said separable part and saidmain part; and wherein said cavity of said papermaking mold isconfigured so that said cavity is in conformity to a contour of saidpulp preform comprising a main part having an open neck and a body witha diameter greater than a diameter of said open neck and a separablepart having a flange and connected to an edge of the said open neck. 6.The apparatus for producing a pulp molded article according to claim 5,wherein said cavity of said papermaking mold is configured so that saidseparable part has an upright wall standing from a periphery of saidflange.
 7. An apparatus for carrying out the method of producing a pulpmolded article according to claim 4 comprising: a heating mold having acavity of a prescribed shape; means for putting a pulp preform formed bya wet papermaking process into said heating mold; an expandable pressingmember configured to be inserted into said preform; means for insertingsaid pressing member; means for feeding a prescribed fluid into saidpressing member; means for removing said preform from said heating mold;and means for cutting said preform at a joint between said separablepart and said main part, and wherein said cavity of said heating mold isconfigured so that said cavity is in conformity to a contour of saidpulp preform comprising a main part having an open neck and a body witha diameter greater than a diameter of said open neck and a separablepart having a flange and connected to an edge of the said open neck. 8.The apparatus for producing a pulp molded article according to claim 7,further comprising: a papermaking mold having a cavity of a prescribedshape; means for feeding a pulp slurry to said cavity; and means forfeeding a pressurizing fluid to said preform formed in said cavity. 9.The apparatus for producing a pulp molded article according to claim 8,is wherein said cavity of said papermaking mold is configured so thatsaid separable part has an upright wall standing from a periphery ofsaid flange.
 10. A method of producing a pulp molded article comprising:feeding a pulp slurry to a cavity of a papermaking mold having aprescribed cavity shape to form a pulp preform on a papermaking surfaceof said cavity such that said preform comprises a main part having anopen neck and a body with a diameter greater than a diameter of saidopen neck and a separable part having a flange and connected to an edgeof said open neck; feeding a pressurizing fluid into said preform todewater said preform; removing said preform from said papermaking mold;putting said preform into a cavity of a heating mold having a prescribedcavity shape; inserting an expandable pressing member into said preformfrom a side of said separable part; feeding a prescribed fluid into saidpressing member to expand said pressing member thereby to dry saidpreform while pressing said preform by the expanded pressing membertoward said papermaking surface; removing the dried preform from saidheating mold; and then cutting said preform at a joint between saidseparable part and said main part.
 11. A method of producing a pulpmolded article comprising: forming a preform having a prescribed shapeby a wet papermaking process; putting said preform into a cavity of aheating mold having a prescribed cavity shape; inserting an expandablepressing member into said preform; feeding a prescribed fluid into saidpressing member to expand said pressing member thereby to press saidpreform by the expanded preform toward a surface of said cavity to shapesaid preform into a main part having an open neck and a body with adiameter greater than a diameter of said open neck and a separable parthaving a flange and connected to an edge of said open neck; removing aresulting preform comprising said main part and said separable part fromsaid heating mold; and then cutting said preform at a joint between saidseparable part and said main part, and wherein said pressing member isinserted into said preform from a side of said separable part.